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Direct current arc fault circuit interrupter, direct current arc fault detector, noise blanking circuit for a direct current arc fault circuit interrupter, and method of detecting arc faults

a direct current arc fault and circuit interrupter technology, applied in emergency protective circuit arrangements, semiconductor devices, etc., can solve the problems of dc electrical generating modules that do not provide series or parallel arc fault protection, fuses are essentially useless in pv power systems, and all the connecting feed conductors between pv generating modules and return conductors are unprotected from arcing events or short circuits of many

Active Publication Date: 2011-06-16
EATON INTELLIGENT POWER LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

The patent describes a circuit and method for detecting arcing in direct current circuits, which can cause damage and potentially start a fire. The circuit uses alternating current sensors and filter circuits to detect peak current signals, which are then compared to predetermined thresholds to determine if an arcing event has occurred. The circuit can be used in a circuit interrupter to quickly trip open the separable contacts in response to an arcing event. The technical effect of this invention is to provide a reliable and effective way to detect and respond to arcing events in direct current circuits, which can help to prevent damage and minimize the risk of fire.

Problems solved by technology

It is believed that there is no known mechanism in photovoltaic (PV) (e.g., photovoltaic; solar electric) systems to detect arcing faults and stop strings or string arrays from generating energy under an in-circuit (series) fault or a short circuit fault (e.g., without limitation, a parallel arc), which can result in a fire.
For example, fuses at the load end of a string do not prevent this fault.
It is believed that all of the connecting feed conductors between the PV generating modules and the return conductors are un-protected from arcing events or short circuits of many kinds
It is believed that known strings and arrays of DC electrical generating modules do not provide series or parallel arc fault protection.
It is believed that fuses are essentially useless in PV power systems since such fuses are sized at 125% and typically must open at 150% of full load current, while the maximum short circuit current for PV arrays does not exceed 100% of full load current.
Therefore, string fuses are useless for providing protection from a forward feed fault, or bus faults that occur above the string fuses.
It is believed that fuses also cannot provide protection from an arcing fault.
Module DC / DC converters can turn off power to exposed connectors, but are believed to lack a detection mechanism for faults.
Otherwise, there is no protection or control at the PV module and, therefore, no way to turn off the potential generated by the PV modules other than to block the light and prevent illumination of the silicon diodes of the PV module by covering the PV modules, an impractical strategy in the field.
However, there is no protection for series arcing faults or many short circuits between the positive and negative feed wires or ground.

Method used

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  • Direct current arc fault circuit interrupter, direct current arc fault detector, noise blanking circuit for a direct current arc fault circuit interrupter, and method of detecting arc faults
  • Direct current arc fault circuit interrupter, direct current arc fault detector, noise blanking circuit for a direct current arc fault circuit interrupter, and method of detecting arc faults
  • Direct current arc fault circuit interrupter, direct current arc fault detector, noise blanking circuit for a direct current arc fault circuit interrupter, and method of detecting arc faults

Examples

Experimental program
Comparison scheme
Effect test

example 1

[0067]Referring again to FIG. 5, the example DC AFCI 60 can be for a string (e.g., without limitation, DC string 26 of FIG. 2 having a string voltage of about 24 VDC to about 600 VDC at greater than about 7 A maximum) or a DC EGM, such as the PV module 22 of FIG. 2. The DC AFCI 60 includes the current sensor 102, an analog front end 104 and the processor 72 (e.g., without limitation, microprocessor) that monitors the sensed string current 108 and reports the same (e.g., without limitation, through communication port 110). The DC AFCI 60 can monitor current (I) and voltage (V). The processor 72 can include a number (e.g., one, some or all) of an over current protector routine 112, an arc fault protector routine 114 (e.g., series; parallel) and a reverse current protector routine 116, which can provide various protection / alarm functions, as well as string performance (e.g., open; low output). The example DC AFCI 60 also includes the separable contacts 62 controlled by the processor 72...

example 2

[0070]FIG. 6A shows a routine 150 providing DC arc fault detection, control and protection for the processor 72 of FIG. 5. The routine 150 enables the processor 72 to detect a series arc fault or a parallel arc fault, such as a parallel arc to ground or to the return conductor. In FIG. 6A, the AC (frequency) thresholds of step 156 (thresholds 74 of FIG. 4) are valid for both series and parallel arcs.

[0071]The routine 150 starts at 152 after which the processor 72 is initialized at 153 and an integer, i, is set equal to zero. Next, at 154, a suitable delay (e.g., without limitation, 3 mS; any suitable delay time) is introduced. Then, at 155, the signal level is measured or input in all AC (high frequency) ranges of interest. Next, at 156, it is determined if a plurality (e.g., without limitation, three; any suitable plural count) of the peak current signals (e.g., 266 of FIG. 7) exceed the corresponding predetermined thresholds 74. If not, then at 158, the integer, i, is decremented ...

example 3

[0079]Referring to FIG. 7, a DC arc fault circuit interrupter (AFCI) 250 is shown including three current transformers (CTs) 252,254,256 employing three example predetermined, relatively narrow frequency bands (f1, f2, f3) to avoid known noise sources (e.g., without limitation, from a specific inverter (e.g., 34 of FIG. 2) with known switching frequencies). For example, the inductance (of the inductive coils L1, L2, L3) and the capacitance (of the capacitors C1, C2, C3) can be provided for suitable center frequencies of interest (e.g., without limitation, 1 kHz, 4 kHz, 10 kHz).

[0080]In this example, the number of filter circuits 68 is a plurality of filter circuits, the number of alternating current signals is a plurality of alternating current signals (e.g., one for each of the narrow frequency bands (f1, f2, f3)), the number of peak detectors 70 of the analog processing circuit 258 is a plurality of peak detectors, and the number of peak current signals 266 provided to the process...

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Abstract

A direct current arc fault circuit interrupter includes separable contacts and a trip circuit to trip open the contacts. The trip circuit includes a number of alternating current sensors structured to sense a current flowing through the separable contacts, a number of filter circuits cooperating with the AC current sensors to output a number of AC signals, a number of peak detectors cooperating with the filter circuits to output a number of peak current signals, and a processor cooperating with at least the peak detectors. The processor inputs the number of peak current signals as a plurality of peak current signals or inputs the number of peak current signals and determines the plurality of peak current signals. The processor also determines if the peak current signals exceed corresponding predetermined thresholds for a predetermined time, and responsively causes the contacts to trip open.

Description

BACKGROUND[0001]1. Field[0002]The disclosed concept pertains generally to arc fault detection and, more particularly, to direct current arc fault circuit interrupters. The disclosed concept also pertains to direct current arc fault detectors, noise blanking circuits for direct current arc fault circuit interrupters, and methods of detecting arc faults.[0003]2. Background Information[0004]It is believed that there is no known mechanism in photovoltaic (PV) (e.g., photovoltaic; solar electric) systems to detect arcing faults and stop strings or string arrays from generating energy under an in-circuit (series) fault or a short circuit fault (e.g., without limitation, a parallel arc), which can result in a fire. For example, fuses at the load end of a string do not prevent this fault. For example, arcs consume energy that does not transfer to an inverter or load.[0005]Known practice places a protective device (i.e., a fuse) at the load end of a string, in one feed conductor (e.g., wire;...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): H02H3/50
CPCH01L31/02021Y02E10/56H02H7/20H02H1/0015H02H1/04
Inventor HASTINGS, JEROME K.ZUERCHER, JOSEPH C.PAHL, BIRGERPIER, BRIAN THOMASGISSKE, EDWARD T.
Owner EATON INTELLIGENT POWER LTD
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